That is pretty much the argument that he's making and it's certainly an option. That being said and as you note, most GMs who give up high draft picks (specifically, multiple high round picks) aren't going to do so for the possibility of a one year rental when he hits free agency in 15 months.
I am still of the belief that Jimmie's potential contract is not such a big issue. If I'm a GM I go to him and say,
"Jimmy, I'm thrilled to have you. We just invested a huge amount of draft capital to get you here. We think you can be our franchise QB, and quite frankly, my success at my job is going to be directly affected by how you do at yours. We both have a lot on the line.
That being said, as the season goes on, we both hope that it goes well enough that we can get an extention done before the season ends, based on that structure we talked about with your agent last week. But as you know this is a production based business. You are not a rookie. Come in, work hard, and produce, and you WILL be paid.....sooner rather than later".
I still believe having a year left on JG's contract when he is traded is a big value factor. Think about it. Even if they can't reach a deal, the combined cost of Jimmy's contract in 2017 and then franchise him in 2018 is STILL a big bargain, if he turns out to be as good as we think.
I still go nuts when I hear from the Felger's of the world that the Pats will be lucky to get low first for him...if that. Ridiculous. If you are a GM and you need a QB, then you are a GM who is going to be looking for a job if you don't find one FAST. The problem is that there ARE no first round QB's in this draft, and even if there were, YOU won't last long enough to watch him develop if there were, and you got extremely lucky and he was good. You need a QB ready to go. And the best prospect in THAT market is JG. 50% of all first round picks bust out, and even some of the ones that become players, never live up to a high first round expectations. What good is that draft pick doing you if you are out looking for work because you didn't have a QB.
THAT's why the Pats will get a pick that is going to surprise some.